glretrace: glClampColor targets are enums.

These can be GL_FALSE, GL_TRUE or GL_FIXED_ONLY.

This patch is not perfect as GL_FALSE and GL_TRUE are now displayed as GL_ZERO and GL_ONE.
cmake: Use POSITION_INDEPENDENT_CODE target property.

For convenience libraries, instead of mucking about with compilation
flags.

Suggested by Chad Versace on Waffle mailing list.
gltrace: Don't bother distinguishing between glVertexAttribPointerARB and glVertexAttribPointer.

These are aliases, and both part of OpenGL 2.0.
gltrace: Simplify _need_user_arrays.
dispatch: Cleanup.
d2d1trace: Fix library name.
os: Mark os::abort as noreturn.
gltrace: Fix glGetDebugMessageLog fallback.
os: Silence ‘noreturn’ function does return warning.
gldispatch: Don't inline dispatch of GL functions.

Inlining the dispatch functions lead to slow compilation times,
and probably slower runtime due to code bloat.
scripts: Install apitrace.PIXExp too.
trace: Make it easier to debug COM object wrapper.
dxgitrace: Serialize WKPDID_D3DDebugObjectName strings.
specs: Add EXT_create_context_es_profile bits.
specs: Add WGL_EXT_create_context_es_profile bits.
glretrace: Introduce ProfileDesc.

To simplify context profile characterisation.
glretrace: Abstract eglBindAPI inside glws.

Instead of calling eglBindAPI directly.
glretrace: Allow to create GLES1 GLX contexts.
gltrace/glretrace: Fake all debug functions.

And not just the glGet*.

Fixes issue #281.